This research program is aimed at the development of a safe and effective vaccine against sexually transmitted diseases caused by chlamydia trachomatis. The objectives of the proposed studies are to investigate the immunogenicity and efficacy of microparticles for oral immunization and bioadhesive microspheres for intravaginal immunization, both containing a selected oligopeptide immunogen from C. trachomatis. In this Phase I pilot study, we will: (1) Design and assess a microparticle-based oral vaccine for its ability to induce potent vaginal and systemic immune responses against a synthetic peptide immunogen corresponding to a neutralizing antibody domain on the relevant serovars of C. trachomatis. (2) Design and assess a microsphere-based intravaginal vaccine for its ability to induce potent vaginal and systemic immune responses to the peptide immunogen from C. trachomatis. (3) Determine the ability of oral and intravaginal vaccines to induce protective immunity against chlamydial challenge in a relevant mouse model of infection and undertake preliminary studies to investigate the potential of combined oral/intravaginal immunization to induce optimal immune responses in the genital tract of female mice.